D-mannose is a sugar monomer of the aldohexose series of carbohydrates. D-mannose is a C-2 epimer of glucose, and has the following structure:

D-mannose is important in human metabolism, especially in the glycosylation of certain proteins.
The Palm kernel is the edible fruit of the oil palm tree. It yields two distinct oils—palm oil and palm kernel oil. The pulp left after oil is rendered is formed into “palm kernel cake”, and is typically used either as high-protein feed for dairy cattle or burned in boilers to generate electricity for palm oil mills. A byproduct which is produced in conjunction with the production of palm oil is palm kernel cake (PKC), which is sometimes referred to as either palm kernel meal (PKM) or palm kernel expeller (PKE) depending upon the method employed in the extraction of the oil from the palm kernel. The process for producing the palm kernel cake is described in an article by Tang Thin Sue, entitled, “Quality and Characteristics of Malaysian Palm Kernel Cakes/Expellers.” In general, the PKE byproduct is produced by a screw-pressing and filtration process, rather than a higher cost solvent extraction process.
The PKC or PKE contains a moderate level of crude protein (14.5 to 19.6 percent), but a high level of fiber (13-20 percent) and a poor amino acid profile which is deficient in lysine, methionine and tryptophan, and as such is considered a moderate quality food for ruminant mammals (having two-stomachs, such as cows) and not suitable for monogastric animals. The fiber of the PKE is primarily hemicelluloses consisting of mannans, moderate amounts of cellulose and small amounts of polysaccharides. The mannan portion of the PKE can range from between 25 to 32 percent. Because the mannan is hard and water insoluble and has a complex chemical structure, a combination of enzymes including mannosidases, galactosidases, glucosidases, and xylanases are required to release the potential fermentable sugars to improve the nutritive value of PKE to be of use to monogastric animals. Enzyme treatment of PKE for the improvement of the nutritive value of PKE is further described in an article by Saenphoom, et al., entitled, “Effect of enzyme treatment on Chemical composition and production of Reducing Sugars in Palm (Elaeis guineenis) Kernel Expeller.”
U.S. Pat. No. 6,896,918 discloses a mannose containing palm kernel meal can be obtained by reacting a mannan degrading enzyme or an acid catalyst with palm kernel meal. A mixture of palm kernel meal, a mannan degrading enzyme and water thus prepared is reacted at the optimal temperature for the enzymatic activity to effect the reaction, and a wet composition is obtained. Mannose or mannosides (mannobiose, mannotriose, and mannooligosaccharides) are generated with the amounts depending on the reaction time in the wet composition. When the reaction time is between 24 to 72 hours, up to about 10-25 parts by weight of mannose are produced per 100 parts by weight of the material palm kernel meal, depending upon the amount of enzyme used. The resulting wet product, without further water removal, can be used as a feedstuff additive for preventing Salmonella infection. The palm kernel meal after the enzyme reaction contains considerable amount of water and the development of mold and fungi can occur during distribution and use, if untreated. In which case, the wet palm kernel meal may be dried to a water content of equal to or less than 10% by methods such as fluidized-bed drying or the like. Further, when highly purified mannose is required as materials for fine chemicals, it may be extracted and purified with an adequate catalyst such as water etc.
Simulation of a moving sorbent bed is described in U.S. Pat. No. 2,985,589 (Broughton et al.), which is mentioned above. In accomplishing this simulation, it is necessary to connect a feedstream to a series of beds in sequence, first to bed no. 1, then to bed no. 2, and so forth for numerous beds, the number of beds often being between 12 and 24. These beds may be considered to be portions of a single large bed whose movement is simulated. Each time the feedstream destination is changed, it is also necessary to change the destinations (or origins) of at least three other streams, which may be streams entering the beds, such as the feedstream, or leaving the beds. The moving bed simulation may be imply described as dividing the bed into series of fixed beds and moving the points of introducing and withdrawing liquid streams past the series of fixed beds instead of moving the beds past the introduction and withdrawal points. A rotary valve used in the Broughton process may be described as accomplishing the simultaneous interconnection of two separate groups of conduits.
U.S. Pat. No. 4,412,866 describes an example of the operation of chromatographic simulated moving bed (or sometimes called “SMB”) method to separate the components of a feed stock. A resin bed is divided into a series of discrete vessels, each of which functions as a zone within a circulation loop. A manifold system connects the vessels and directs, in appropriate sequence to (or from) each vessel, each of the four media accommodated by the process. Those media are generally referred to as feed stock, eluent, extract and raffinate, respectively. As applied to a sugar factory, a typical feed stock is a lower purity sucrose solution, the eluent is water, the extract is an aqueous solution of sucrose and the raffinate is an aqueous solution containing non-sucrose, such as salts and high molecular weight compounds. The simulated moving bed disclosed by the '866 patent is of the type sometimes referred to as a “continuous SMB.”
An example of a batch chromatographic method for the purification of sucrose is described in the disclosure of U.S. Pat. No. 4,359,430, which utilizes sucrose feedstocks derived from sugar beets at purities of approximately 7% to 60% sucrose. See also, e.g., U.S. Pat. No. 5,466,294, which utilizes a “soft raw syrup” as a feedstock to a chromatographic method which is not in a high purity form at a less than 89% purity sucrose on a dry solids basis, i.e., approximately 11% non-sucrose impurities.
US Patent Publication US2003/0222021 discloses a chromatographic separation process for recovering mannose with high purity using a chromatographic separation including a resin which is at least partially in a Ba2+ form resin and a resin which is other than Ba2+ form.
Methods are sought for a more efficient method of producing d-mannose from palm kernel meal.